The invention relates to external fixators, and in particular to a bone-fixator configuration wherein spaced first and second bone-screw mounting members are connected end-to-end via one or more ball-and-socket joints which are releasably lockable to preserve a given orientation of one mounting member to the other mounting member.
U.S. Pat. No. 4,988,349 (now reissue U.S. Pat. No. Re. 34,985) describes an external fixator of the character indicated, having particular application to the fixation of fragments of a fractured bone associated with the wrist. Such fractures are complex, and it is unnecessarily difficult to resort to internal fixation techniques. Moreover, the external fixation of such fractures is also tedious, if the surgeon is to achieve and fix a precise fit of the fracture ends to each other. Said patent partially solves the problem by providing a central spacer element, each end of which has releasably lockable universal ball-joint connection to the end of a different one of the respective bone-screw mounting members.
But each ball-joint connection has universal action, and it is awkward, and in some cases difficult, to make a correctly oriented and clamped setting of each ball-joint, to best serve the surgeon's purposes in fixation of a given wrist-related fracture, particularly if limited wrist articulation is to be afforded during part of the period for fracture healing.